Single-cylinder circular knitting machine for manufacturing socks and stockings or the like

ABSTRACT

The single-cylinder circular knitting machine has a vertically arranged needle cylinder with a skirt defining a plurality of axial grooves. Each groove slidingly accommodates a needle. A platen is arranged coaxially above the needle cylinder, and a plurality of radial grooves is defined therein. Each one of the radial grooves accommodates a hook which is movable by the action of actuation cams which can be engaged, during rotation of the platen about its axis, with a heel of the hooks, from a position in which the hooks are retracted in the platen to an extraction position, and vice versa. The machine is provided with a hook locking device which is arranged proximate to the platen and is controllably engageable with the hooks to keep them in the retracted position in the platen.

BACKGROUND OF THE INVENTION

The present invention relates to a single-cylinder circular knittingmachine for manufacturing socks and stockings and in particular to amachine with high safety against the accidental escape of the hooks fromthe platen.

As is known, single-cylinder circular knitting machines generallycomprise a needle cylinder which is arranged vertically and on whoseskirt a plurality of axial grooves is defined; each one of said groovesslidingly accommodates a needle.

Needle actuation cams are arranged around the needle cylinder and definepaths within which a heel of the needles, which protrudes radially fromthe related groove, engages. The shape of said paths is such as to give,during the rotation of the needle cylinder about its axis with respectto the needle actuation cams, a reciprocating movement to the needlesalong the related groove. By means of this reciprocating movement, theneedles form knitting by cyclically picking up a thread provided at afeed of the machine and forming new loops linked to the previouslyformed loops of knitting.

Above the needle cylinder there is usually a platen which is arrangedcoaxially to the needle cylinder and has a plurality of radial grooves,each accommodating a hook.

Each hook is provided with one or more heels which protrude upward fromthe radial grooves and engage paths defined by cams for the actuation ofthe hooks which face the platen in an upward position. The actuation ofthe platen with a rotary motion about its axis, together with the needlecylinder, causes the various hooks to follow these paths, which areshaped so as to move the hooks from a retracted position in the platento an extraction position in which the hooks protrude radially withtheir tip from the platen.

The radial grooves of the platen are offset with respect to the axialgrooves of the needle cylinder so that each hook can protrude from theplaten between two contiguous needles.

The use of the hooks during the operation of these machines is limitedto a particular process. In the production of stockings, the use of thehooks is usually limited to the initial step of the process, i.e. duringthe forming of the upper edge of the stocking, when the hooks areextracted from the platen to form a tubular border in cooperation withthe needles. During the forming of the remaining part of the stocking,the hooks generally remain unused and are kept in the platen in aretracted position.

In order to avoid complicating the profile of the hook actuation camsexcessively, said cams are limited to a cam which causes the extractionof the hooks and to a cam which causes their retraction, said cams beingmutually angularly spaced with respect to the axis of the platen.

For this reason, when the extraction of the hooks is not required, saidhooks could protrude accidentally from the platen due to the centrifugalforce generated by the rotation of the platen together with the needlecylinder. In order to avoid this unwanted movement, which would causeunwanted alterations in the process in progress, the stem of the hooksis appropriately bent laterally in one or more points of its extensionso that by resting against the lateral walls of the related radialgroove, it withstands by friction the centrifugal force to which it issubjected.

This solution, which has long been adopted in the field ofsingle-cylinder circular knitting machine for manufacturing socks andstockings, has some problems particularly in modern machines, which canreach high speed rotation.

In fact, in order to overcome the high centrifugal forces which act onthe hooks it is necessary to obtain an increasingly higher frictionbetween the hooks and the radial grooves of the platen. This frictionforce, whose effect is desirable when the hooks must not be used,becomes disadvantageous when the hooks must be actuated in one directionor the other along the radial grooves. In this occasion the frictionforce in fact opposes the action of the cams, and the higher thefriction force, the higher the force exchanged between the heels of thehooks and the hook actuation cams. Since the wear of the heels isdirectly correlated to said force, there is a rapid wear of the heels ofthe hooks, particularly in machines operating at high speed, whichnecessitates frequent maintenance interventions in order to replace thehooks.

Furthermore, the friction force which acts on the hooks generates anegative torque on the platen which compels one to oversize therotational connection between the needle cylinder and the platen inorder to avoid accidental displacements between the platen and theneedle cylinder, which are particularly dangerous during the extractionof the hooks, since they would cause the breakage or damage of theneedles and hooks.

The friction force, which is intentionally increased by bending thehooks or with equivalent contrivances, has so far necessitated theadoption of high-strength mechanical connections between the needlecylinder and the platen and has discouraged the adoption of other typesof connection.

SUMMARY OF THE INVENTION

The aim of the present invention is to solve the above describedproblems by providing a single-cylinder circular knitting machine,particularly for manufacturing socks and stockings wherein it ispossible to safely avoid the accidental escape of the hooks of theplaten despite an extremely modest friction between the hooks and theradial grooves of the platen.

Within the scope of this aim, an object of the invention is to provide amachine which can reach high operating speeds without incurring problemsregarding the retention of the hooks in the grooves of the platen.

Another object of the invention is to provide a machine wherein the wearof the heels of the hooks is reduced.

A further object of the invention is to provide a machine with a platenwhich can be rotated about its own axis with a reduced torque withrespect to that required by conventional machines.

Yet another object of the invention is to provide a machine wherein therotational linkage between the needle cylinder and the platen can beprovided in an extremely simple and reliable manner.

This aim, these objects and others which will become apparenthereinafter are achieved by a single-cylinder circular knitting machineparticularly for manufacturing socks and stockings, comprising avertically arranged needle cylinder having a skirt, a plurality of axialgrooves defined in said skirt, each groove slideably accommodating aneedle, a platen arranged coaxially above said needle cylinder, aplurality of radial grooves defined in said platen, each one of saidradial grooves slideably accommodating a hook, cams being provided forthe actuation of said hooks, said cams facing said platen in an upwardposition and defining paths engageable by at least one heel of saidhooks which protrudes upward from said radial grooves in order to movesaid hooks, upon the rotation of said platen about its own axis withrespect to said actuation cams, from a position in which said hooks areretracted in the platen to an extraction position, and vice versa,characterized in that it comprises a hook locking device arrangedproximate to said platen and being controllably movable from an inactiveposition, whereat said device does not interfere with said hooks, to anactive position, whereat said device engages said hooks in saidretracted position to retain them in said retracted position, and viceversa.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the invention will becomeapparent from the description of a preferred but not exclusiveembodiment of a machine according to the invention, illustrated only byway of non-limitative example in the accompanying drawings, wherein:

FIG. 1 is a schematic axial sectional view of a single-cylinder circularknitting machine for manufacturing socks and stockings, with the hooklocking device in active position; and

FIG. 2 is an axial sectional view of the machine, taken similarly toFIG. 1, with the hook locking device in inactive position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the above figures, the machine according to theinvention, generally designated by the reference numeral 1, comprises aneedle cylinder 2 arranged vertically and comprising a skirt, having aplurality of axial grooves 3 defined therein; each one of said groovesslideably accommodates a needle 4 which has a heel 4a protrudingradially from the grooves 3.

A plurality of needle actuation cams, of a per se known type which isnot illustrated for the sake of simplicity, is arranged around theneedle cylinder 2; said cams define paths in which the heels 4a of theneedles engage.

Said paths have ascending and descending portions, and the needlecylinder 2 can be actuated in a known manner with a rotary motion aboutits own axis 5 with respect to the needle actuation cams so that thesliding of the heels 4a along the paths defined by said cams actuatesthe needles in a direction which is parallel to the axis 5 and makesthem cyclically protrude upward from the needle cylinder, in order toengage a thread which is fed to them at the feeds or drops of themachine, and retract into the needle cylinder, forming new loops ofknitting linked to the previously formed loops which are unloaded fromthe needles and descend toward the inside of the needle cylinder.

A platen 6 is arranged above the needle cylinder 2, and its axiscoincides with the axis 5 of the needle cylinder 2.

A plurality of radial grooves 7 is defined on the upper face of theplaten 6; each one of said grooves slidingly accommodates a hook 8provided with one or more heels 8a which protrude upward from the platen6 and engage hook actuation cams 9 facing the platen 6 in an upwardposition. Said cams 9 have portions which move toward the axis 5 andportions which move away from said axis, so that by actuating the plate6 with a rotary motion together with the needle cylinder 2, the hooks 8pass, when required, from a retracted position in the platen 6 to anextraction position in which they protrude radially with their tip fromthe platen 6, and vice versa.

The radial grooves 7 of the platen 6 are angularly offset about the axis5 with respect to the axial grooves 3 of the needle cylinder 2, so thateach hook 8 can protrude from the platen between two contiguous needles4 without interfering with them.

According to the invention, the machine comprises a hook locking device,generally designated by the reference numeral 10, which is arrangedproximate to the platen 6 and can move controllably from an inactiveposition, in which it does not interfere with the hooks 8, to an activeposition, in which it engages the hooks 8 in a retracted position so asto retain them in said retracted position despite the action ofcentrifugal force which acts on them during rotation of the platen 6about the axis 5.

More particularly, the locking device 10 comprises a locking element 11which is slidably accommodated in the platen 6 along the axis 5. Saidlocking element 11 has a disk-like portion 12, whose axis coincides withthe axis 5, arranged inside the platen 6 below the hooks 8. Thedisk-like portion 12 has a perimetric edge 13 which is raised andengageable with a recess 14 appropriately provided on the back of thehooks 8 proximate to their end directed toward the axis 5. The recess 14is located at the perimetric edge 13 when the related hook is in theretracted position in the platen 6.

The locking element 11 is accommodated in a seat 15 defined in theplaten 6, and springs 16 are interposed between the lower face of thelocking element 11 and the bottom of said seat 15; said springs act onthe locking element to keep its perimetric edge 13 engaged with thehooks 8.

The locking element 11 is centrally provided with a sleeve 17 axiallyslideably mounted on a shaft 18 which passes coaxially through theplaten 6.

The shaft 18 is rigidly coupled to the platen 6 in rotation about theaxis 5, and proximate to the sleeve 17 it is traversed by a hole 19which is perpendicular to the axis 5 and has a transverse cross-sectionwhich is elongated parallel to the axis 5. The sleeve 17 is transverselycrossed by a secondary shaft 20 which also passes through the hole 19 soas to rigidly couple the locking element 11 to the shaft 18 in rotationabout the axis 5 but allow it to slide axially with respect to the shaft18 by an axial extent which is delimited by the width of the hole 19 inthe direction which is parallel to the axis 5.

As an alternative, the hole 19 can have a circular cross-section with adiameter which is greater than that of the secondary shaft by an amountwhich is greater than the height of the perimetric edge 13.

Actuation means act on the locking element 11 in order to move it fromthe active position to the inactive position against the biasing actionof the springs 16.

The shaft 18 is hollow and the actuation means comprise a rod 21 whichis slideably accommodated inside the shaft 18 for sliding movement alongthe axis 5. The lower end of the rod 21 rests on the secondary shaft 20,whereas its upper end protrudes from the shaft 18. Actuation means 22,for example of the pneumatic, electromagnetic or mechanical type, orequivalent means are arranged proximate to the upper end of the rod 21and controllably act on said rod 21 so as to cause its translatorymotion along the shaft 18 and move the locking element 11 from theactive position to the inactive one.

The actuation means 22 are operatively connected to an electroniccontrol element 50 which supervises the operation of the machine andactuates the locking device 10 according to the requirements ofproduction.

Preferably, the platen 6 is connected to the needle cylinder 2 inrotation about the axis 5 by means of a magnetic coupling.

More particularly, the shaft 18 extends below the platen, and its lowerend is associated with a cylindrical support 23 arranged inside theneedle cylinder 2, proximate to the upper end thereof.

The skirt of the cylindrical support 23 faces the inner surface of theneedle cylinder 2 and first magnetically active inserts 24, fixed tosaid cylindrical supports 23, are distributed about the axis 5. Theinserts 24 face secondary magnetically active inserts 25 which areapplied to the inner surface of the needle cylinder and are arrangedcorrespondingly. In this manner, if the needle cylinder 2 is actuatedwith rotary motion about the axis 5, the platen 6 also rotates.

The displacement between the needle cylinder and the platen, duringacceleration or deceleration imparted to the needle cylinder, isnegligible and is not in any case such as to produce interferencebetween needles 4 and hooks 8, since the negative torque which opposesthe rotation of the platen 6 is extremely modest as a consequence of theadoption of the device 10 for locking the hooks 8, which allows toreduce the friction between the hooks 8 and the radial grooves 7 tominimal levels.

Conveniently, the cylindrical support 23 is produced in two mutuallycoaxial parts, respectively 26 and 27, to allow the correct mutualtiming of the needle cylinder 2 and the platen 6 during assembly of themachine.

More particularly, the part 26 is arranged inside the part 27 and isrigidly fixed to the shaft 18.

The part 26 is provided with an upper disk-like end 26a with at leastone radial groove 28 against which the upper end of the part 27 rests.

At least one axial hole 29 is defined in the part 27 and rotatablyaccommodates an eccentric pivot 30 which engages the groove 28 with oneof its ends. By rotating the eccentric pivot 29 about its axis, with thepart 27 not fixed to the part 26, the angular position of the part 27 ischanged with respect to the part 26. The locking of the part 27 on thepart 26 is provided by means of screws 31 which cross, with such a playas to allow a partial rotation of the part 27 with respect to the part26 as required during timing, axial holes 32 which are defined in thepart 27.

The screws 31 engage threaded holes defined in the upper disk-like end26a, and a cover 33 is interposed between the head of the screws 30 andthe part 27. In addition to the holes for the passage of the screws 31,holes at each eccentric pivot are defined in the cover 33, for thepassage of a fixing screw 34 which is screwed in the eccentric pivot 30after performing timing in order to lock it.

The operation of the machine according to the invention is as follows.

During the execution of processes which do not require the use of thehooks 8, the locking device 10 is kept in an active position by theaction of the springs 16. In this position, the locking element 11 keepsthe hooks 8 in a retracted position in the platen 6 with absolutesafety, even with high rotation speeds of the platen 6 (FIG. 1).

It should be noted that the locking element 11 rotates together with theplaten 6 about the axis 5, and thus no wear occurs between the lockingelement 11 and the hooks 8.

When the use of the hooks 8 is required, the electronic control element50 of the machine activates the actuator 22 which, by pressing on therod 21, disengages the locking element 11 from the hooks 8, overcomingthe action of the springs 16 (FIG. 2). In this manner, the hooks 8 canbe actuated as in conventional machines to take part in the knitting inprogress.

When the hooks 8 must be again disengaged from work, the actuator 22 isdeactivated so that the springs 16 return the locking element 11 to theactive position (FIG. 1).

In practice it has been observed that the machine according to theinvention fully achieves the intended aim, since by virtue of the hooklocking device it achieves a highly reliable retention of the hooksinside the platen even with high-speed rotation of the platen and withextremely modest friction between the hooks and the platen.

A further advantage of the machine according to the invention is that itis possible to use a connection which adopts a magnetic coupling, whichis considerably simpler than conventional couplings between the platenand the needle cylinder, again as a consequence of the fact that thefriction between the hooks and the platen can be extremely modest andthat the negative torque which contrasts the rotation of the platen istherefore also modest.

The machine thus conceived is susceptible to numerous modifications andvariations, all of which are within the scope of the inventive concept;furthermore, all the details may be replaced with technically equivalentelements.

In practice, the materials employed, so long as they are compatible withthe specific use, as well as the dimensions, may be any according to therequirements and the state of the art.

We claim:
 1. Single-cylinder circular knitting machine particularly formanufacturing socks and stockings, comprising, a vertically arrangedneedle cylinder having a skirt and an axis, a plurality of axial groovesdefined in said skirt, a needle slideably accommodated in each of saidgrooves, a platen arranged coaxially above said needle cylinder, aplurality of radial grooves defined in said platen, hooks slideablyaccommodated in said radial grooves, at least one heel provided on eachof said hooks and protruding from said radial grooves, actuation camsfacing said platen and defining paths, said paths being engageable bysaid at least one heel of each of said hooks for moving said hooks uponrotation of said platen about said axis with respect to said actuationcams, between a retraction position whereat said hooks are retracted insaid radial grooves of said platen and an extraction position whereatsaid hooks are extracted from said radial grooves of said platen, saidmachine further comprising a hook locking device, said hook lockingdevice being arranged proximate to said platen and controllably movablebetween an inactive position, whereat said hook locking device does notinterfere with said hooks, and an active position, whereat said hooklocking device engages said hooks in said retracted position forretaining said hooks in said retracted position.
 2. Machine according toclaim 1, wherein said hook locking device comprises a locking element,said locking element being accommodated in said platen and controllablyslideable parallel to said axis for passing between said active positionand said inactive position.
 3. Machine according to claim 2, whereinsaid hook locking element is rigidly coupled to said platen in rotationabout said axis.
 4. Machine according to claim 2, wherein said hooklocking element has a disk-like portion, said disk-like portion beingarranged coaxially to said platen and below said hooks and having araised perimetric edge, and wherein said hooks each have an end directedtowards said axis, and a back defining a recess, said recess beingdefined proximate to said end, said raised perimetric edge beingengageable with said recess.
 5. Machine according to claim 1, whereinsaid locking device comprises a locking element, said locking elementbeing centrally provided with a sleeve, said sleeve being slideablealong a shaft, said shaft being arranged coaxially to said platen andrigidly coupled thereto in rotation about said axis.
 6. Machineaccording to claim 5, further comprising means for delimiting axialsliding movement of said locking element along said shaft.
 7. Machineaccording to claim 6, wherein said means for delimiting axial slidingmovement of said locking element along said shaft comprise a secondaryshaft, said secondary shaft transversely crossing said sleeve and beingslideably accommodated in a hole, said hole crossing said shafttransversely and having a transverse cross-section, said transversecross-section being elongated in a direction parallel to said axis. 8.Machine according to claim 1, further comprising actuation means, saidactuation means acting on said locking element for moving said lockingelement between said active position and said inactive position. 9.Machine according to claim 7, wherein said shaft is hollow and has anupper end, and wherein said actuation means comprise a rod having alower end, said rod being slideably accommodated in said shaft andextending from said hole accommodating said secondary shaft andprotruding from said upper end of said shaft, said rod being axiallymovable along said shaft for acting with said lower end on saidsecondary shaft, whereby to move said locking element between saidactive position and said inactive position against elastic means. 10.Machine according to claim 9, wherein said locking element has a lowerface, and wherein said platen has defined therein a seat having a bottomand slideably accommodating said locking element, said elastic meansbeing interposed between said lower face of said locking element andsaid bottom of said seat.
 11. Machine according to claim 1, wherein saidplaten is connected to said needle cylinder in rotation about said axisby magnetic coupling means.
 12. Machine according to claim 5, whereinsaid platen is connected to said needle cylinder in rotation about saidaxis by magnetic coupling means, said magnetic coupling means comprisingfirst magnetically active inserts and secondary magnetically activeinserts, said secondary magnetically active inserts being connected tosaid skirt of said needle cylinder and being distributed around saidaxis proximate to an upper end of said needle cylinder, said shafthaving an extension and a cylindrical support, said extension protrudingdownwardly from said platen, said cylindrical support being connected tosaid extension and arranged inside said needle cylinder facing saidsecondary magnetically active inserts, said first magnetically activeinserts interacting with said secondary magnetically active inserts andbeing distributed around said axis and fixed on said cylindricalsupport.
 13. Machine according to claim 12, further comprising means forangular position adjustment of said cylindrical support about said axiswith respect to said shaft.